36% of homes for sale in Phoenix are vacant, either due to speculators getting caught holding the bag or people who have bought and moved to new homes without finding a buyer for their previous home. Average time to sell (for those houses that are actually selling) is 94 days, versus 73 days a year ago.

Zillow seemed to have stopped updating Phoenix-area home prices on September 11, but they've now given an update with October 25 data, and my home's "zestimate" value has dropped by 3.6% since the September 11 data.

If house prices are going up, they're going to keep going up, so you should buy.

If house prices are going down, we're near a bottom, so you should buy.

It's kind of like the excuses used by purveyors of quack remedies that don't do anything--if you get better, it worked. If you get worse, you need to increase your dosage until you get better. If you die, you didn't use enough quickly enough. Since disease progression has ups and downs, they can explain any outcome in a way favorable to their remedy.